摘要
对GCr15轴承钢进行170℃时效处理,使用SEM、TEM、XRD等手段对其表征,研究了这种钢在时效过程中碳化物的演化行为及其对性能的影响。结果表明,在840℃淬火后再在230℃回火,钢的硬度不低于59HRC,冲击韧性大幅度提高,钢中的残余奥氏体基本上消除,可保障其170℃的性能和尺寸稳定性。在时效过程中发生的碳原子配分和碳化物析出,使钢基体中碳的浓度、晶格畸变、微区应力应变先降低后稳定,过渡碳化物向非共格的渗碳体转变和粗化。这两个因素的耦合作用使钢的硬度降低、冲击韧性先升高后降低。马氏体的碳脱溶和碳化物类型的转变相互协调,使钢时效1000 h到2000 h间硬度有所回升。为了提高时效过程中钢的显微组织和性能的稳定性,淬火后又进行了深冷处理以引入高密度缺陷,促进了回火和时效过程中碳元素的配分,使析出的碳化物细小弥散并抑制了其在时效过程中的长大与粗化。深冷处理使碳化物的长大速率由298 nm^(3)/h降低到229.5 nm^(3)/h,在一定程度上延缓了性能的衰退、提高了GCr15轴承钢在真空干泵高温环境中的性能稳定性。
The evolution behavior of carbides in GCr15 bearing steel and its influence on the impact toughness during long-term aging at 170℃ have been investigated by means of SEM,TEM,and XRD,aiming to meet the requirements of vacuum dry pump bearings.The results demonstrate that after quenching at 840℃ and the tempering at 230℃,the hardness of GCr15 steel remains above 59 HRC with minimal retained austenite,which is favorable to the enhancement of performance and dimensional stability for the steel at 170℃.During the aging process,carbon atom partitioning and carbide precipitation lead to a decrease in carbon concentration,lattice distortion and micro-zone stress strain of the matrix,while transitional carbides precipitate,coarsen and then transform into non-coherent cementite.The resultant effect of these microstructural variation is a reduction in material hardness,while the impact toughness initially increasing and then decreasing.However,the cooperative effect of the decarbonization of martensite and carbide type transformation makes hardness of steels remain stable or even increase a little in between 1000 h and 2000 h during the aging process.To improve the microstructure and performance stability during the aging process,cryogenic treatment was conducted after quenching.The introduction of high-density defects promotes effective carbon distribution during tempering and aging,which gives rise to uniform distribution and size control of fine carbides.Cryogenic treatment reduces the carbide growth rate from 298 nm^(3)/h to 229.5 nm^(3)/h,which delays the performance decline effectively and makes the GCr15 bearing steel satisfied with demands of vacuum dry pump bearings.
作者
刘震寰
李勇翰
刘洋
王培
李殿中
LIU Zhenhuan;LI Yonghan;LIU Yang;WANG Pei;LI Dianzhong(Institute of Metal Research,Chinese Academy of Sciences,Shenyang 110016,China;School of Materials Science and Engineering,University of Science and Technology of China,Shenyang 110016,China)
出处
《材料研究学报》
EI
CAS
CSCD
北大核心
2024年第2期130-140,共11页
Chinese Journal of Materials Research
基金
中国科学院区域重点项目A类(KFJ-STS-QYZD-2021-20-002)。
